Synthesis of N-aminopyrazoles by Fe(II)-catalyzed rearrangement of 4-hydrazonomethyl-substituted isoxazoles

Isomerization of 5-(2H-Azirin-2-yl)oxazoles: An Atom-Economic Approach to 4H-Pyrrolo[2,3-d]oxazoles

“…Whereas heating compounds 2r and 2s with vinyl and chloromethyl substituents resulted in complete resinification of the reaction mixtures. All new compounds were characterized by 1 H, 13 C-NMR and HRMS methods. Moreover, the structure of 3d was also confirmed by singlecrystal X-ray diffraction analysis (Figure 3).…”

“…Melting points were determined on a melting point apparatus SMP30 (Research Park, Saint Petersburg State University, Saint Petersburg, Russia). 1 H-NMR (400 MHz) and 13 C-NMR (100 MHz) spectra were recorded on a Bruker AVANCE 400 spectrometer (Research Park, Saint Petersburg State University, Saint Petersburg, Russia) in CDCl 3 or DMSO-d 6 . Chemical shifts (δ) are reported in parts per million downfield from tetramethylsilane (TMS, δ = 0.00).…”

“…1 H-NMR (CDCl 3 , 400 MHz): δ 1.27 (t, 3H, J = 7.6 Hz), 1.34 (s, 9H), 2.70 (q, 2H, J = 7.6 Hz), 2.90 (s, 1H), 6.80 (s, 1H). 13 2-Phenyl-5-(3-phenyl-2H-azirin-2-yl)oxazole (2h). Compound 2h [27] was prepared following the general procedure GP-A from azirine 1a (500 mg, 2.7 mmol), benzonitrile (29 mL, 284 mmol) and Rh 2 (oct) 4 (2.1 mg, 0.027 mmol) in DCE (250 mL) in 302 mg (43% yield, after column chromatography on silica (light petroleum/ethyl acetate, 7:1 (v/v)) as a brown oil.…”

“…1 H-NMR (DMSO-d 6 , 400 MHz): δ 1.40 (t, 3H, J = 7.6 Hz), 2.92 (q, 2H, J = 7.6 Hz), 3.84 (s, 3H), 6.30 (d, 1H, J = 1.6 Hz), 6.92-6.95 (m, 2H), 7.44-7.47 (m, 2H), 9.03 (s, 1H). 13…”

“…Compound 2k was prepared following the general procedure GP-A from azirine 1c (150 mg, 0.62 mmol), benzonitrile (9.5 mL, 93 mmol) and Rh 2 (oct) 4 (5 mg, 0.0062 mmol) in DCE (130 mL) in 84 mg (43% yield, after column chromatography on silica (light petroleum/ethyl acetate, 7:1 (v/v)) as a yellow oil. 1 H-NMR (CDCl 3 , 400 MHz): δ 1.79-1.87 (m, 6H), 1.99-2.07 (m, 6H), 2.12-2.16 (m, 3H), 2.93 (s, 1H), 7.01 (s, 1H), 7.41-7.45 (m, 3H), 7.93-7.96 (m, 2H) 13. C{ 1 H}-NMR (CDCl 3 , 100 MHz): δ 24.1 (CH), 27.5 (CH), 35.7 (C), 36.4 (CH 2 ), 38.3 (CH 2 ), 125.2 (CH), 126.1 (CH), 127.5 (C), 128.8 (CH), 130.1 (CH), 152.4 (C), 160.5 (C), 170.5 (C).…”